1. Field
One embodiment of the invention relates to an information processing apparatus including a display unit which has light emitting elements as a light source and a luminance control method applied to the information processing apparatus.
2. Description of the Related Art
Recently, portable terminal devices each including a display unit such as a liquid crystal display (LCD) which has light emitting elements such as light emitting diodes (LEDs) as a light source are developed. The light emitting efficiency of the LED was low in the past, but now the light emitting efficiency thereof is sufficiently corrected.
In Jpn. Pat. Appln. KOKAI Publication No. 2001-76525, an illumination equipment in which luminance irregularity is corrected by alternately arranging LEDs connected to a first power supply control circuit and LEDs connected to a second power supply control circuit is disclosed.
Further, in Jpn. Pat. Appln. KOKAI Publication No. 2002-100485, the technique for attaining a white-light emitting source by use of a red LED, green LED and blue LED is described.
Luminance irregularity occurs since the characteristics of LEDs are variously changed, and therefore, it is considered to adjust the luminance by feeding back a current in order to correct the luminance irregularity. According to the above document, the cathodes of the LEDs connected to the first power supply control circuit and the cathodes of the LEDs connected to the second power supply control circuit are grounded. If the magnitude of the current is measured, the current will be set equal to an average magnitude of a current flowing through a circuit which includes the LEDs connected to the first power supply control circuit and a current flowing through a circuit which includes the LEDs connected to the second power supply control circuit. As a result, it is difficult to perform the precise feedback operation. Therefore, it is difficult to correct the luminance irregularity of the display unit.